SpongeBob
If you thought that living in with your mom in your 20s or being in a trailer was weird: HE lives in a PINEAPPLE!
This sea sponge is the physical embodiment of optimism and naivete, as he always wants to be a source of positivity for the people he cares deeply for. Whether it be his best friend Patrick Star, his abrasive and annoyed neighbor Squidward, his boss and owner of the Krusty Krab Mr Krabs, or his Texan friend Sandy, despite him not being the strongest, or the most bold, he's known well around Bikini Bottom - for better, or for... not better. His hobbies mainly include bubble-blowing and jellyfishing.
Patrick
He lives under a rock, he does nothing all day, and he thinks that mayonnaise is an instrument. What a great friend!
Patrick being SpongeBob's friend is a bit of an oddity, as they are in a way polar opposites. While SpongeBob is pretty composed, smart and down-to-earth most of the time (less Patrick's influence gets in the way), he on the other hand... is dim-witted and a lazy slob who can get angered or jealous very easily. Despite this, he still tries to overcome his negative traits and be in the moment when it's most needed. His favorite hobbies are doing nothing all day.
This crustacean you see here is the one behind one of the biggest resturants in Bikni Bottom - the Krusty Krab. Being the owner of such a big place in Bikini Bottom makes his infactuation with money stronger than it already has been! He loves money so much to the point where it's like a second daughter right next to his beloved Pearl the Whale, making him stingy. Sometimes he can care for other things, such as his prized frycook SpongeBob, but most of the time his brain runs on the chase for the almighty dollar! His hobbies are being clawsy with his cash, finding new ways to fill his pockets, and, as he calls it, "counting the booty". 
Think of the most snobby, self-centered and nihilistic person you know. Now, take that person and throw them into the sea with a 9-5 job and a failed dream. That's who Squidward is, and that's how he's been since the day he was born. This octopus usually thinks that he's better than everyone else, mainly due to his dream of being a clarinet player despite his flawed skills; in reality most people are annoyed by simply being in his vicinity. The only people who put this difference aside and appreciate him are SpongeBob and Patrick, his two neighbors (this is mainly due to them being naive), which he is constantly pestered by through their own stupidity. While he doesn't absolutely loathe them, he wouldn't be complaining if they moved out overnight!
Ever had a friend from a different country or state? Well... what if they were that, but also a squirrel who could build an entire dome under the sea along with being a toughie, having great karate skills, being able to get through tough situations, having lots of experience with science, AND having the thickest Texan accent you can think of? That's Sandy Cheeks for ya! Most of the time she's usually just a friend to others in Bikini Bottom, but other times she can be the source of chaos. On occasion, she can be the "straight man" of a situation, usually zipping in when SpongeBob and Patrick (or anyone else she knows for that matter) has a problem they can't fix by themselves or are just acting dumb (lol).
I promise you, Krabs! One day or another I'll rule the world. There will be a day where my little resturant is filled with far more customers than you'll ever see in your whole life, and all of the pawns in Bikini Bottom will look up to ME and ME alone. You may sink in your riches now, but once I get my hands on that secret formula it'll ALL BE MY OWN MAKING! Why else would I have went to college?
